Sound producer



United States Patent 3,284,796 SOUND PRODUCER Vincent S. Borsattino, 4160 Pierce St; Chursel E. Marker, 793 Indiana St.; and Harold L. Morris, 1338 Morton St.; all of Gary, Ind.

Filed Get. 30, 1961, Ser. No. 148,515 3 Claims. (Cl. 340384) This invention relates generally to electronic sound producing devices and, more particularly, to transistor operated electronic warning devices.

It is often desirable to provide a warning of dangerous or abnormal conditions. For example, when materials handling equipment is driven in reverse it is desirable to provide a warning noise to those in the immediate vicinity. Conventionally this type of warning is given by standard automobile horns operated by a relay and actuated when the vehicle is shifted into reverse. The standard horns are prone to malfunctioning and failure after a relatively short period of time. Further, the tone of an automobile horn is not an unpleasing tone and it is a steady tone during the entire time that the vehicle is operated in reverse. It is more desirable to have a very unpleasing tone for these warning devices because of the greater likelihood of causing an immediate awareness of this tone to the hearer. It is also more desirable to have an intermittent tone rather than a steady tone which will cause an immediate and continuous response in the bearer.

It is therefore .a principal object of this invention to provide a fully electronically controlled and produced intermittent harsh tone.

Yet another object of this invention is to provide an electronic warning device which will produce an intermittent harsh audible sound from a steady current.

A more specialized object of this invention is to provide a transistor powered timer and tone generator which will produce an intermittent non-sinusoidal signal from steady direct current.

A feature of this invention is the provision of a multivibrator which provides a non-sinsoidal signal, which multi-vibrator is controlled by an electronic switching circuit.

Another feature of this invention is the provision of an electronic circuit for the production of harsh sounds into which can be inserted a microphone for voice communication.

Other objects and advantages of the invention will become apparent from the following description and accompanying drawings, in which:

FIGURE 1 shows the circuit of an electronic sound producing device according to this invention; and

FIGURE 2 shows the circuit of FIGURE 1 with a microphone inserted therein.

The sound producing device of this invention includes a transistor powered timer or switching circuit adapted to deliver an interrupted signal from a constant source of DC. current. A transistor powered multivibrator tone producer is coupled to the timer circuit and adapted to produce a non-sinusoidal signal responsive to the signal delivered from the timer circuit. A transistor driver circuit is coupled to the tone producer circuit and an amplier with a speaker is coupled to the driver circuit to produce an audible harsh tone from the non-sinusoidal signal of the multivibrator.

Referring now to FIGURE 1, the sound producer is shown in a typical environment with various components of a vehicle being shown schematically. A battery is shown and designated as which preferably is the battery of the vehicle upon which the sound generator is mounted. The negative side of the battery is connected 3,284,796 Patented Nov. 8, 1966 to a switch 11 Which is closed by gear shift 12 when the gear shift is in the reverse position. A first conductor 13 is connected to the switch 11 and a second conductor 14 is connected to the positive side of the battery 10. A resistor 15 is provided in the conductor 14 if the voltage of the battery is above the normal operating range of the sound producing device. A fuse 16 is provided in the conductor 14 to protect the circuit from excessive current and a diode 17 is provided to prevent damage to the circuit if reverse polarity is accidentally applied.

The sound producing device includes a switch and timer circuit 20. The timer circuit 20 includes a first transistor 21 and a second transistor 22. The first transistor 21 has an emitter electrode 23 connected to the conductor 14 and the transistor 22 has an emitter electrode 24 also connected to the conductor 14. Transistor 21 has a base electrode 25 connected to the conductor 13 through resistor 26 and transistor 22 has a base electrode 27 connected to the conductor 13 through resistor 28. The resistor 28 has a greater resistance than the resistor 26, the reason for which will be described presently.

The transistor 21 has a collector electrode 29 which delivers an output signal when the transistor 21 is conducting. A capacitor 30 is coupled across the collector electrode 29 of transistor 21 and the base electrode 27 of transistor 22. Transistor 22 has a collector electrode 31 which is coupled to the base electrode 25 of the transistor 21 through capacitor 33. The collector electrode 31 of transistor 22 is connected to conductor 13 through resistor 34.

When the gear shift 12 is shifted into the reverse posi tion. switch 11 will be closed and steady will be applied to conductors 13 and 14. Current will flow and a positive condition will exist between the emitter electrode 23 and the collector electrode 29 of the transistor 21. This will cause transistor 21 to be conductive and a signal will 'be produced at collector electrode 29 of transistor 21. Since the value of resistor 28 is greater than the value of resistor 26, the transistor 22 will be inoperative. Current from the collector electrode 29 will charge capacitor 30. The charge on capacitor 30 will build up until it reaches a point where it counterbalanccs the negative stress on transistor 22 caused by resistor 28 at which point transistor 22 will begin to conduct. Current from the collector electrode 31 of the transistor 22 will charge capacitor 33. The charge on capacitor 33 will build up until it reaches a point where it overcomes the bias on transistor 21 caused by resistor 26 at which point the transistor 21 becomes non-conductive. Current will then cease to flow from the collector electrode 29. When current ceases to flow from the collector electrode 29, the capacitor 30 will lose its charge through resistor 28 and through the components of multivibrator circuit 49, as will become apparent, and transistor 22 will become nonconductive. Current will then cease to flow from the collector electrode 31 and the capacitor 33 will lose its charge through resistors 26 and 34. As the charge drains from capacitor 33 a point will be reached when the transistor 21 again becomes conductive and the cycle will repeat itself. Thus it can be seen that the timer circuit 20 causes an intermittent positive signal in collector electrode 29.

The multivibrator circuit 40 is coupled to the timer circuit 20 and includes a pair of transistors 41, 42 having respectively emitter electrodes 43, 44, each connected to collector electrode 29 of transistor 21. The transistors 41, 42 have base electrodes 45, 46 connected to conductor 13 through resistors 47, 48 respectively. Transistors 41, 42 have respectively collector electrodes 49, 50 each adapted to deliver an output signal. A capacitor 51 is coupled between collector electrode 49 of transistor 41 and base electrode 46 of transistor 42. A capacitor 52 is similarly coupled between the collector electrode 50 of transistor 42 and the base electrode 45 of transistor 41. Collector electrodes 49, 50 are connected to the conductor 13 through resistors 53, 54 respectively.

When a signal is produced in collector electrode 29 the signal is applied simultaneously to emitter electrodes 43, 44. Due to inherent differences in the components of the multivibrator circuit, one or the other of the transistors 41, 42 will first become conductive and the other will remain non-conductive. Assuming that transistor 41 first becomes conductive a signal will be produced at the collector electrode 49, which at the first instant will charge capacitor 51. The charge on capacitor 51 will bias transistor 42 into a nonconductive state. Capacitor 51 will begin to lose its charge through resistors 48 and 53 until base electrode 46 of transistor 42 is negative enough to cause transistor 42 to conduct. A signal will then be produced in collector electrode 50 of transistor 42 which will cause capacitor 52 to charge biasing transistor 41 into a nonconductive state. Capacitor 52 will then lose its charge through resistors 54 and 47 and transistor 41 will again reach its conductive point. This type of multivibrator action is well known in the art. Thus, an oscillating circuit is provided with a non-sinusoidal signal produced at collector electrode 49. The signal produced at collector electrode 49 is an audiofrequency tone. The timer circuit 20 and multivibrator circuit 40 together constitute a repetition rate generator.

A driver circuit 60 is coupled to the multivibrator circuit 40. The driver circuit 60 includes a transistor 61 having a base electrode 62 connected to collector electrode 49 of transistor 41 through a capacitor 63. The base electrode 62 of transistor 61 is also connected to collector electrode 29 of transistor 21 through a resistor 64. The transistor 61 includes an emitter electrode 65 connected to collector electrode 29 of transistor 21. During the time that a signal is produced at collector electrode 29 a bias is applied to transistor 61 and hence transistor 61 is synchronous with transistor 21. The signal produced at collector electrode 29 produces an audio frequency tone signal in the multivibrator circuit 40 and this tone passes through capacitor 63 which causes transistor 61 to operate as a class B amplifier. Capacitor 63 also blocks D.C. current from passing to base electrode 62. Hence, the driver circuit 60 amplifies the signal from the multivibrator 40 and delivers the amplified signal at collector electrode 66 of transistor 61.

A conventional amplifying circuit 70 is coupled to the driver circuit 60. The amplifying circuit 70 includes a transformer 71 having a primary coil 72 coupled between collector electrode 66 and conductor 13. The amplifier circuit 70 includes a push-pull circuit 73 having a pair of transistors 74, 75. The transistors 74, 75 have base electrodes 76, 77 respectively connected to opposite ends of secondary coil 78 of the transformer 71. Emitter electrodes 79, 80 of the transistors 74, 75 are connected to the center of the secondary coil 78 of transformer 71 through resistor 81. Resistor 81 is a low value resistor or thermistor to prevent thermal run away of transistors 74, 75. Collector electrodes 82, 83 of the transistors 74, 75

are connected to opposite ends of primary coil 84 of a transformer 85. Secondary coil 86 of the transformer 85 is connected to a speaker 87. Also, the center of the secondary coil 78 of transformer 71 is connected to the center of primary coil 84 of transformer 85 through resistor 88. The amplified signals from collector electrode 66 of transistor 61 are further amplified by the amplifier circuit 70 in a Well known manner and are broadcast intermittently as harsh audible tones by speaker 87.

Typical values of the components of the circuit are given below in Table I. These values are illustrative only and are in no way limitations on the invention.

4 TABLE I Transistors 21, 22, 41, 42,

61, 74 and 75 PNP Junction.

Resistor 26 1,500 ohms.

Resistors 34, 53, 54 and 88 1,000 ohms.

Resistors 47 and 48 100,000 ohms.

Resistor 28 22,000 ohms.

Resistor 64 100 ohms.

Resistor 81 4 ohms.

Capacitors 30 and 33 100 ufd.

Capacitors 51 and 52 .1 ufd.

Capacitor 63 5 ufd.

Transformer 71 100 ohms 50 ma. D.C. to

15 ohms CT 200 to 2000 CRS.

Transformer 48 ohms 550 ma. D.C. to

16 ohms CT.

With the values given in Table I the timer circuit 20 will provide alternately a positive on signal and a zero off condition at collector electrode 29 at a rate of about 60 times per minute. This means that there is a signal at collector electrode 29 for about half a second and no signal for about half a second. During the half a second that there is a signal the multivibrator circuit 40 will produce a substantially square wave signal with many harmonics at a frequency of about 1500 cycles per second. This signal amplified by driver circuit 60 and amplifier 70 will produce a harsh sounding tone at speaker 87 for the half second of the signal at collector electrode 29 and the speaker will produce no sound during the half second that there is no signal. Thus, the sound generator of this invention produces an intermittent harsh tone during the entire period that the gear shift 12 is in the reverse position. This intermittent harsh tone is produced from a steady supply of D.C. current with no mechanical switching required. As long as a steady current is applied to the conductors 13 and 14 an intermittent sound will be produced. This intermittent sound is produced with no moving parts in the circuits and with all switching being done electronically through transistors. The sound producer of this invention is relatively free of maintenance since there are no moving mechanical parts and various tones 'and rates of tone production can be selected by varying the values of the components of the circuit. A circuit with the values given in Table I has been successfully operated continuously for 24 hours at temperatures as low as 40 F. and as high as 145 F.

Referring now to FIGURE 2, a microphone 90 is shown in the circuit. The microphone 90 has a first terminal 92 connected to the positive side of battery 10 through diode 17 and a second terminal 96 connected to a normally open contact 98. A contact 94 is provided which when closed energizes solenoid 102. Contacts 94, 98 are closable by button 100. Solenoid 102 operates contacts 104, 106 and 10 8. Each of the contacts has a first position and a second position, each normally being in its first position and movable to the second position when solenoid 102 is energized.

In its first position contact 104- is open and in its second position connects the negative side of the battery to the center of primary coil 84 or transformer 85, and to primary coil 72 of transformer 71. Contact 106 in its first position connects collector electrode 49 of transistor 41 to the base electrode 62 of transistor 61 through capacitor 63. In its second position contact 106 discon nects collector electrode 49 from base electrode 62 and connects the base electrode 62 to terminal 96 through contact 98. In its first position contact 108 connects collector electrode 29 of transistor 21 to emitter electrode 65 of transistor 61. In its second position contact 108 disconnects collector electrode 29 from emitter electrode 65 and connects emitter electrode 65 to conductor 14. A microphone load resistor 110 is provided between contact 98 and conductor 13 for current control. sistor has a value of about 1000 ohms.

As can be seen in FIGURE 2 when contacts 94 and 98 are in their normally open position the solenoid 102 is not energized and contacts 104, 106 and 108 will be in the normal first positions. When the vehicle is shifted in reverse, the circuit will function identically as the circuit of FIGURE 1. However, if button 100 is pushed it will close contacts 94 and 98. When contact 94 is closed it will energize solenoid 102 which will shift contacts 104, 106 and 108 into their second positions. This will disconnect the transistor 61 from timer circuit and from the multivibrator circuit and connect the microphone to the transistor 61 and also provide a constant supply of power to its emitter electrode 65 and the amplifier circuit 70. Hence, sound delivered to the microphone is amplified by the driver circuit 60 and amplifier circuit 70 and broadcast from speaker 87. When button 100 is released contacts 94 and 98 return to their normally open position which will deenergize solenoid 102 and contacts 104, 106 and 108 will return to their first positions. It can be seen that whether or not the gear shift 12 is in reverse when button 100 is pushed the microphone will be operably connected into the circuit and if the gear shift 13 is in reverse the microphone circuit will override the repetition rate generator.

While several embodiments of our invention have been shown and described it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

We claim:

1. An intermittent sound generator comprising in combination, a transistor switching circuit having means adapt- This reed to receive a constant direct current from a power source and provide an intermittent signal, said switching circuit including a first transistor normally conductive and a second transistor normally nonconductive, first capacitor means responsive to the first transistor and adapted to urge the second transistor into conductivity after a predetermined amount of time of conductivity of the first transistor, second capacitor means responsive to the second transistor and adapted to urge the first transistor into nonconductivity after a predetermined amount of time of conductivity of the second transistor, and resistor means positioned to return each of said transistors to their normal state after a predetermined amount of time, whereby said first transistor is alternately conducting and nonconducting, a tone generator coupled to said switching circuit having means adapted to generate an audio frequency tone when a signal is received by the tone generator from the switching circuit, driver means operably connected to said tone generator to amplify the tone generated, a microphone selectably connectable to said driver means, and means to disconnect the tone generator from the driver means when the microphone is connected thereto, power amplifying means operably connected to said driver means, and sound producing means adapted to broadcast the amplified tone operably connected to said amplifying means, whereby interrupted sound is produced from a constant direct current.

:2. An intermittent sound generator comprising in combination, a transistor powered switching circuit having means adapted to receive a constant direct current from a power source and provide an intermittent signal, a transistor multivibrator coupled to said switching circuit, said multivibrator including electrically operated means to produce audio frequency signals responsive to a signal received from said switching circuit, driver means including a driver transistor coupled to said multivibrator adapted to amplify a signal received therefrom, means to energize said driver transistor from the signal delivered by the switching circuit, a microphone selectably connectable to said driver means and means to disconnect the switching circuit and the multivibrator from said driver means when the microphone is connected thereto, power amplifying means coupled to said driver means, and sound producing means adapted to broadcast the amplified tone coupled to said amplifying means, whereby interrupted sound is produced from a steady direct current.

3. An intermittent sound generator comprising in combination, a switching circuit adapted to receive a constant direct current from a power source and provide an intermittent signal, said switching circuit including a first normally conductive transistor and a second normally nonconductive transistor, a first capacitor responsive to said first transistor and adapted to urge said second transistor into conductivity after a predetermined amount of time of conductivity of the first transistor, a second capacitor responsive to said second transistor and adapted to urge the first transistor into nonconductivity after a predetermined time of conductivity of the second transistor, resistor means positioned to return each of said transistors to their normal condition after a predetermined amount of time, a transistor powered multivibrator coupled to said switching circuit, said multivibrator including electrically operated means to produce audio frequency signals responsive to a signal received from said switching circuit, driver means including a driver transistor coupled to said multivibrator adapted to amplify a signal received therefrom, said driver transistor being connected to said switching circuit and energized by a signal therefrom, a microphone selectably connectable to said driver means and means to disconnect the switching circuit and the multivibrator from said driver means when the microphone is connected thereto, a power amplifier means coupled to said driver means, and speaker means coupled to said power amplifier means, whereby interrupted sound is produced from a steady direct current.

References Cited by the Examiner UNITED STATES PATENTS 2,455,472 12/1949 Curl et al 340384 X 2,576,585 11/1951 Fleming 340-384 2,898,587 8/1959 Nye 34084O 2,910,688 10/1959 Kelley et al. 340384 2,910,689 10/ 1959 Grace 340384 2,926,347 2/ 1960 Thiele 33152 2,974,424 3/1961 Roberts 340--384 2,977,584 3/1961 Seigel 340384 2,988,708 6/1961 Schmidt 340384 2,994,765 8/1961 Adam 33147 3,085,211 4/1963 Jensen et al. 33152 3,101,447 8/1963 Smith 33147 3,108,597 10/1963 Moss et a1 340-384 NEIL C. READ, Primary Examiner.

BENNETT G. MILLER, Examiner.

W. C. GLEICHMAN, T. A. ROBINSON,

Assistant Examiners. 

1. AN INTERMITTENT SOUND GENERATOR COMPRISING IN COMBINATION, A TRANSISTOR SWITCHING CIRCUIT HAVING MEANS ADAPTED TO RECEIVE A CONSTANT DIRECT CURRENT FROM A POWER SOURCE AND TO PROVIDE AN INTERMITTENT SIGNAL, SAID SWITCHING CIRCUIT INCLUDING A FIRST TRANSISTOR NORMALLY CONDUCTIVE AND A SECOND TRANSISTOR NORMALLY NONCONDUCTIVE, FIRST CAPACITOR MEANS RESPONSIVE TO THE FIRST TRANSISTOR AND ADAPTED TO URGE THE SECOND TRANSISTOR INTO CONDUCTIVITY AFTER A PREDETERMINED AMOUNT OF TIME OF CONDUCTIVITY OF THE FIRST TRANSISTOR, SECOND CAPACITOR MEANS RESPONSIVE TO THE SECOND TRANSISTOR AND ADAPTED TO URGE THE FIRST TRANSISTOR INTO NONCONDUCTIVITY AFTER A PREDETERMINED AMOUNT OF TIME OF CONDUCTIVITY OF THE SECOND TRANSISTOR, AND RESISTOR MEANS POSITIONED TO RETURN EACH OF SAID TRANSISTORS TO THEIR NORMAL STATE AFTER A PREDETERMINED AMOUNT OF TIME, WHEREBY SAID FIRST TRANSISTOR IS ALTERNATELY CONDUCTIVITY AND NONCONDUCTING, A TONE GENERATOR COUPLED TO SAID SWITCHING CIRCUIT HAVING MEANS ADAPTED TO GENERATE AN AUDIO FREQUENCY TONE WHEN A SIGNAL IS RECEIVED BY THE TONE GENERATOR FROM THE SWITCHING CIRCUIT, DRIVER MEANS OPERABLY CONNECTED TO SAID TONE GENERATOR TO AMPLIFY THE TONE GENERATED, A MICROPHONE SELECTABLY CONNECTABLE TO SAID DRIVER MEANS, AND MEANS TO DISCONNECT THE TONE GENERATOR FROM THE DRIVER MEANS WHEN THE MICROPHONE IS CONNECTED THERETO, POWER AMPLIFYING MEANS OPERABLY CONNECTED TO SAID DRIVER MEANS, AND SOUND PRODUCING MEANS ADAPTED TO BROADCAST THE AMPLIFIED TONE OPERABLY CONNECTED TO SAID AMPLIFYING MEANS, WHEREBY INTERRUPTED SOUND IS PRODUCED FROM A CONSTANT DIRECT CURRENT. 